Wasatch Cache National Forest

In partnership with: The Friends of the Utah Avalanche Forecast Center, Utah Department of Public Safety Division of Comprehensive Emergency Management, Salt Lake County, and Utah State Parks

The Utah Avalanche Center Home page is: http://www.avalanche.org/~uac/

Avalanche advisory

Tuesday, March 18, 2003

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Good Morning. This is Bruce Tremper with the Forest Service Utah Avalanche Center with your backcountry avalanche and mountain weather advisory. Today is Tuesday, March 18, 2003, and it’s 7:30 in the morning.

Current Conditions:

Last night it continued to snow with the Cottonwood Canyons picking up another 5-7 inches of 10 percent water weight snow. This makes 10-13 inches of snow in the past 24 hours. The Park City side of the range and parts of the Ogden area mountains got about half that amount and Logan and Provo area mountains got very little snow overnight. As usual for this winter, very little snow fell below about 7,000’. Storm totals since Friday in the Cottonwood Canyons are 20-30 inches with a water weight from 2-3 inches. Yesterday, the ridge top winds were from the northwest 20-30 mph and overnight the winds have been out of the north at a more reasonable 10-20 mph. Ridge top temperatures are in the mid teens.

Avalanche Conditions:

For a welcome change, yesterday’s avalanche activity remained just within the new snow as easily-triggered, shallow, soft slabs created by wind deposits. Between three different parties of backcountry skiers in Days and Silver Fork, they were able to trigger perhaps 15-20 of these sensitive wind slabs, mostly intentionally, but occasionally unintentionally. They were breaking mostly 6-8 inches deep, occasionally up to a foot and were 50 to 100 feet wide but one was as much as 250 feet wide. These kinds of fresh, soft wind slabs are much safer to deal with than the monster, deep avalanches we have had for most of the season because fresh, soft slabs tend to be very sensitive, so they tend to break at your feet instead of up above you and they are soft enough to allow for an easier escape. Still they can certainly be dangerous if you’re not prepared. They can easily slam you into trees or burry you in a deep depression such as a gully. (I have details on these slides in the usual locations at 801-364-1591 and at www.avalanche.org – click on Salt Lake, then on Advisories, then on List of Avalanches).

Today you can expect to find similar, widespread, soft, easily-triggered wind slabs on any slope around 35 degrees or steeper with recent deposits of wind drifted snow. Also, there is a slight density inversion in the overnight snow, so you may be able to trigger some soft slabs even in non wind affected terrain. Finally, don’t forget about our season-long horror story of deep, large avalanches breaking into faceted snow buried deep in the snow pack. With all this additional water weight, it’s sure to reactivate a few of these lurking monsters, mostly on steep slopes with a shallow snowpack above 9,500’. Also, a shallower, soft slab avalanche may step down into these deeper weak layers as it descends. Today, be sure to watch your slope steepness very carefully and if you have to jump into something steep, put a good slope cut across it before committing yourself.

Bottom Line (SLC, Park City Area Mountains)

Today there is a MODERATE danger of human triggered avalanches on slopes steeper than 35 degrees with recent wind drifts. On slopes with wind deposits more than a foot deep, the danger is CONSIDERABLE. There is also a MODERATE danger of triggering deeper avalanches on slopes above 9,500 feet that face the north half of the compass plus east facing slopes, especially ones with a shallow snow pack.

Bottom Line: (Ogden and Provo Area Mountains): MODERATE danger on steep slopes steeper than 35 degrees, especially with recent wind drifting.

Western Uintas – call 1-800-648-7433 or click here for weekend and holiday forecasts.

Mountain Weather:

The huge low pressure center is now over Colorado and it is wrapping moisture up around and bringing the flow into Utah from the north. Expect light snow showers through the day today with accumulations around 3-6 inches and continued light snow showers tonight. Ridge top winds should blow today 15-25 from the north, turning northeast by tonight, with ridge top temperatures in the mid teens. Down at 8,000’ the temperatures will be in the mid 20’s today. For the extended forecast: Wednesday looks like it will slowly dry out with ridge top winds from the northeast to east and we should have lingering clouds for Thursday.

The weekend looks nice.

General Information:

As a special treat the more scientifically inclined avalanche nerds out there, our own Ethan Greene will be giving an advanced-level avalanche talk tonight called the “science of avalanches.” This will be at 7:00 pm at REI, which is on 3300 south just off the 215 east side belt route.

Wasatch Powderbird Guides will probably not be flying today. But if they do manage to get out, they will be in Days, Cardiff and Silver Fork with a home run in Grizzly Gulch. For more information call (801) 742-2800.

To report backcountry snow and avalanche conditions, especially if you observe or trigger an avalanche, please leave a message on our answer machine at (801) 524-5304 or 1-800-662-4140, or email to [email protected] or fax to 801-524-6301. The information in this advisory is from the U.S. Forest Service, which is solely responsible for its content. This advisory describes general avalanche conditions and local variations always occur.

I will update this advisory by 7:30 on Tuesday morning.

Thanks for calling!

________________________________________________________________________

National Weather Service - Salt Lake City - Snow.

For an explanation of avalanche danger ratings:

http://www.avalanche.org/usdanger.htm